As a conventional technique to tilt a charged particle beam such as an electron beam or an ion beam on a sample and display a stereoscopic image by a tilted image display on the sample or by a left-right parallax-angle image data, for example, JP-A-2-33843 (Patent Literature 1) and JP-A-2010-9907 (Patent Literature 2) are disclosed. In Patent Literature 1, disclosed is a technique to tilt a charged particle beam at above an objective lens, use an off-axis swing-back action of the objective lens, tilt a charged particle beam on a sample for irradiation, and acquire a tilted image on the sample. Further, in Patent Literature 2, disclosed is a technique to perform a stereoscopic observation by using a charged particle beam device. In the techniques of the literatures, by using an electromagnetic coil, a charged particle beam tilted as much as a left-right parallax-angle is scanned on the sample, stereo pair images of left and right are acquired, and the acquired images are displayed on a 3D-LCD, thereby observing a stereoscopic image in real time.
As an example of a technique to correct a focus, an astigmatism, and a field of view occurring during tilting, JP-A-2010-16007 (Patent Literature 3) discloses. With regard to the astigmatism correction, a combination of a plurality of astigmatism correction values is evaluated to detect an optimum astigmatism correction value. With regard to field-of-view deviation, images before and after a tilt are compared to evaluate a of field-of-view deviation amount and corrected by an image shift or by moving a sample stage.
On the other hand, as a method for observing a sample in which a sample surface itself is tilted larger than the depth of a focus of a charged particle beam, there is used a tilted focus compensation (dynamic focus) function to continuously change the focus of the charged particle beam according to the sample surface tilt and provide an always-focused image. Further, there is used a tilted magnification compensation (tilt compensation) function to change the scan width of the charged particle beam according to the sample tilt angle and scan the charged particle beam on the same region as that before the tilt to acquire an image. These functions are already commercialized.